1. Field of the Invention
The present invention relates to a compound-eye imaging device having an optical imaging system formed of multiple micro optical systems, in which multiple images imaged by the micro optical systems are reconstructed into one image.
2. Description of the Related Art
There has been developed a compound-eye imaging device as a thin camera module to be installed in a cellular phone, a personal computer, or the like. The compound-eye imaging device is mainly composed of: an optical lens array with multiple integrated optical lenses having mutually parallel optical axes; a photodetector array for imaging multiple images (single-eye images) formed by the respective optical lenses of the optical lens army; and an image reconstructing circuit for reconstructing one image from the multiple single-eye images imaged by the photodetector array by using parallax information between the multiple single-eye images.
The multiple single-eye images formed on the photodetector array are sequentially read, one-by-one, along the array by an image reading means formed of a microprocessor having a reading speed which is determined on the basis of a clock generated by the microprocessor, and are reconstructed by the image reconstructing circuit into one image after all the single-eye images are read. Thus, if an attempt is made to display a reconstructed image on a display screen such as an LCD (Liquid Crystal Display) monitor at a relatively high frame rate (number of images renewed per unit time), it is required to increase the reading speed to read the single-eye images from the photodetector array This makes it necessary to increase the clock frequency of the microprocessor, which causes a problem of an increase in power consumption.
Applications of a compound-eye imaging device include e.g. a monitoring camera system, which has a requirement in the frame rate as described below. In normal imaging in which no anomaly is detected, there is no problem with a monitoring camera system to image at a low frame rate and a low resolution. However, in order to track a suspicious moving object once detected by the monitoring camera system, it is necessary to image the object at a high frame rate. Thereafter, when the object slows its movement, while being tracked, making it possible to capture an identifiable image of the object, a high frame rate is not much required.
Rather, it is desirable to image the object at a high resolution so as to determine the outline and detail of the suspicious object. That is, a monitoring camera system is desired to be switched in the following sequence: imaging at a low resolution and a low frame rate→imaging at a low resolution and a high frame rate→imaging at a high resolution and a low frame rate. In other words, in an imaging system for detecting a moving object as represented by the monitoring camera system, it is desirable that the frame rate can be switched to different ones depending on the situation, with the highest frame rate being as high as possible, and that a high resolution imaging can be performed.
According to conventional compound-eye imaging devices, increasing the reading speed (increasing the clock frequency) is the only way to enable a high frame rate and switching between different frame rates. However, the increase in the clock frequency causes an increase in power consumption as described above, so that it is difficult to obtain a sufficiently high frame rate. Furthermore, a technology is known to intermittently remove pixels read by light receiving elements so as to increase the reading speed. However, although this technology enables a high reading rate and a high frame rate, the resultant image may have a false color if pixels of a certain color are not uniformly removed.